RU2492958C2 - Method of making shell ring for vver-reactor body core region - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metallurgy and may be used for producing large-sized shell rings of VVER-1000 reactor bodies. Solid-forged billet is produced, its length making at least that of shell with allowance for machining stock. Billet wall thickness is at least twice as larger as shell ring wall thickness. Samples for mechanical tests are taken on billet inner surface side, at thickness stock. Sampling is executed at the distance from billet ends not smaller than billet thickness. Specimens of said samples are cut so that their length axes are located at the distance from billet inner surface making at least 1/3T and not over 1/2T where T is billet thickness. Rings are cut for production weld check joint on biller inner side.

EFFECT: higher reliability and longer life.

4 dwg, 1 tbl

Description

The invention relates to metallurgy, in particular, to the manufacture of large-sized blanks of reactor vessels of the WWER type.

The VVER-type reactor vessel is a thick-walled cylindrical vessel with an elliptical bottom and a spherical lid, in which the active zone is made of 2 finishing blanks (shells) connected by ring welds (Fig. 1).

With the existing design of the reactor vessel, weld No. 2 welds two finishing blanks (shells) of the reactor vessel core, which fall into the zone of intense neutron irradiation. In addition, welds No. 1 and 3 fall into the intensive irradiation zone. In connection with the foregoing, the life of existing reactors is limited (60 years), which significantly reduces the economic performance of the power plant. In addition, it becomes impossible to increase the reactor power at the design service life due to the degradation of the properties of the weld metal located in the intensive irradiation zone.

It is possible to realize the current trend of increasing the power of a water-water-type nuclear power plant while increasing its service life to 100 years if welding seams are removed from the intensive irradiation zone (Fig. 1a; reactor vessel of the TOI project - Typical Optimized Informatized). This can be realized by using a solid forged blank (shell) of the active zone with a length of 4900 mm for the manufacture of the reactor vessel. In this case, the weld No. 2 is excluded, and the seams 1 and 3 are taken out of the limits of fluence, which affects the mechanical properties during operation (less than 1 · 10 ¹⁸ neutr / m ² ). The solid-forged shell of the core should not be inferior in quality, or possibly exceed those used previously.

For the manufacture of the shell of the active zone of the reactor vessel, a shell blank is used, hereinafter referred to as the blank.

The prototype of the proposed method for the manufacture of billets for the core of the WWER-type reactor vessel is the known method for the manufacture of billets set forth in the Rules for the design and manufacture of mechanical components of nuclear power plants with pressurized water reactors RCC-M [1], in which

- the workpiece is made with a length greater than the length of the workpiece in the finished form, taking into account all the necessary technological allowances, as well as allowances along the length for sampling for mechanical tests and for the manufacture of rings of production control welded joints of PCSS, and a wall thickness equal to the final wall thickness, taking into account technological allowances.

- samples from samples for mechanical testing are cut so that their longitudinal axis are located at a depth equal to ¼ the thickness of the workpiece wall from its inner surface.

Due to the fact that the sampling for mechanical testing and the manufacture of rings for the manufacture of the production control compound (PCSS) takes a significant part of the length of the workpiece, the active zone of the reactor vessel is made of 2 parts interconnected by welding. This seam during operation of the reactor vessel is subjected to intense radiation, which leads to degradation of the properties of the weld metal, which reduces the reliability and service life of the reactor vessel.

If for the manufacture of a one-piece forged core blank, the method described in the prototype is used, then the length of the blank for heat treatment will be about 6 meters (figure 2).

It is currently not possible to produce a forged billet of this length in Russia at any metallurgical plant without significant modernization of the existing forge-and-press and thermal equipment, which will require significant investment. The maximum length of a workpiece that can be manufactured at present in Russian plants is not more than 5 meters.

In addition, the heat treatment of such a preform also presents significant difficulties, since it is necessary to quench such preforms in an upright position in order to ensure uniform cooling during quenching, which is practically impossible to perform for technological reasons.

The technical result of the invention is to increase the reliability and service life of the reactor vessel through the use of a solid-forged billet of the active zone for its manufacture, which makes it possible to move welds out of the intensive irradiation zone, which negatively affects the mechanical properties of the metal and its resistance to brittle fracture.

The technical result is achieved due to the fact that in the proposed method of manufacturing a workpiece of the reactor vessel core (Fig. 3), which includes the manufacture of a workpiece with sampling to control mechanical characteristics and ring cutting for the manufacture of a production test weld joint (PCSS), according to the invention:

- the workpiece is made of solid forged, not less than the length of the shell, taking into account all the necessary technological allowances and a wall thickness exceeding the wall thickness of the shell at least twice,

- sampling for mechanical testing is carried out from the side of the inner surface of the workpiece (from the allowance for the thickness of the workpiece) at a distance from the ends of the workpiece, not less than the thickness, while samples for mechanical testing are cut from the samples so that their longitudinal axes are not spaced less than 1/3 T and not more than 1/2 T from the inner surface of the workpiece, where T is the thickness of the workpiece;

- cutting rings for production control welded joint (PCSS) is produced from the side of the inner surface of the workpiece (from the allowance for the thickness of the workpiece).

With the proposed method for manufacturing a solid forged core blank, the control of mechanical characteristics meets the requirements of regulatory documents [2, 3, 4] and, in addition, is more conservative than in the prototype [1].

In the conditions of JSC "Izhorskiye Zavody" a pilot industrial step blank was manufactured from reactor steel (Fig. 4). The thickness of the profitable end of the billet was 525 mm, and the bottom 320 mm, which corresponded to the thickness of the billet of the active zone of the WWER reactor vessel for heat treatment, taking into account the necessary allowances.

The bottom end imitated the manufacture and sampling by known methods, and the profitable one by the proposed one.

The test results of the mechanical properties are presented in table 1.

As can be seen from the data presented, while ensuring full hardenability, the proposed sampling for acceptance tests is conservative and meets the requirements of regulatory documents. The mechanical properties determined on the samples taken in accordance with known schemes (prototype) and in accordance with the proposed schemes practically coincide.

Technical and economic results compared with the prototype:

The proposed method of manufacturing a solid forged blank of the shell of the active zone of the reactor vessel allows to manufacture a VVER-type reactor vessel of a new design with a reduced number of welds at minimal cost for the technical reconstruction of forge-and-press and thermal equipment available at Russian plants, which provides:

- reducing the manufacturing time of the housing by reducing the number of operations to perform welded joints, including their heat treatment and quality control,

- reducing the volume of control of welded joints of the reactor vessel during operation by reducing their total number,

- reduction in the cost of generated energy.

Information sources

1. Rules for the design and manufacture of the mechanical components of nuclear power plants with pressurized water reactors RCC-M. Section 2 - Materials (part 2). Translation into Russian - June 1988

2. TU 5.961-11060-2008 "Preparations from heat-resistant steel."

3. TU 08 93-013-00212179-2003 "Billets from steel grades 15X2NMFA, 15X2NMFA-A and 15X2NMFA class 1 for vessels, covers and other components of reactor plants."

4. “Standards for calculating the strength of equipment and pipelines of nuclear power plants” (PN AE G-7-002-86). Gosatomenergonadzor of the USSR. - M .: Energoatomizdat, 1989.S. 527.

Claims (1)

A method of manufacturing a blank of a shell of a core of a VVER-type reactor vessel, comprising manufacturing a blank, sampling for mechanical tests and cutting rings for a production test weld, characterized in that the blank is made of forged, not less than the length of the shell, taking into account technological allowances and wall thickness, exceeding the shell wall thickness by at least two times, sampling for mechanical tests is performed from the side of the inner surface of the workpiece from stock the thickness of the workpiece at a distance from the ends of not less than the thickness of the workpiece, while cutting out samples of samples for mechanical testing with the location of their longitudinal axes at a distance from the inner surface of the workpiece not less than 1/3 T and not more than 1/2 T, where T is the thickness of the workpiece, and the rings are cut out for the production control welded joint from the inside of the workpiece.

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